An Ad2 early glycopolypeptide, gp25K, has been purified to homogeneity. A partial amino acid sequence of gp25K will be obtained, in order to map its structural gene on the Ad2 genome. The structure of the oligosaccharide moiety on gp25K will be characterized. A monospecific antiserum against gp25K will be used to study the regulation of the gp25K gene. Mutants in and about the gp25K gene will be isolated and studied.